Frozen sprocket

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New Member

Ive put roughly 1,000 miles on my 7 speed beach cruiser since I install a 49cc motor. I tightened the chain tension because the chain is stretching, became loose where chain was falling off back tire sprocket when going fast over bumpier terrain..
Anyways.. With clutch engaged I can move bike freely but back wheel wont even move when clutch disengaged. Normally I would hear engine compression as I rode it as if no gas...but since the back wheel won't move I'm not sure if it's the drivetrain issue inside the engine behind the sprocket. I've opened cover. Just real greasy and appears to have metal shavings... What might I need to replace? I already ordered new chain and tensioner.
Please help... I put 20 miles a day on it...usually.
P.s. the chain isn't bunched up around the sprocket, as I said it moves when the clutch is engaged but when the clutch is not engaged it doesn't do anything except freeze.
Would the magneto have anything to do with this?

Well-Known Member

clutch not engaged is when the chain should move without turning motor - you have that backwards

if chain and front sprocket and clutch hub all turn when clutch is not engaged, but engaging clutch stops everything, then motor may be seized or some piece of metal got stuck in teeth of the bevel gears - first, take out spark plug and try to turn motor by putting a wrench on nut on rotor

if motor won't turn, take off clutch cover and see if anything is stuck in gear teeth

New Member

clutch not engaged is when the chain should move without turning motor - you have that backwards

if chain and front sprocket and clutch hub all turn when clutch is not engaged, but engaging clutch stops everything, then motor may be seized or some piece of metal got stuck in teeth of the bevel gears - first, take out spark plug and try to turn motor by putting a wrench on nut on rotor

if motor won't turn, take off clutch cover and see if anything is stuck in gear teeth

The cover, over the sprocket where the chain goes, had what appeared to me were metal threads that had came off as shavings with a whole bunch of grease and dirt, so I cleaned it and put it back on... when I pull the lever for the clutch the bike moves, but when I release the lever for the clutch my bike won't move. Unless I lift up the back wheel.
All I did was I couldn't afford the chain tensioner and a new chain right away so I took the hole chain bracket tensioner off and I tighten it by hand and then I put it back on, the Chain had enough play in it but as soon as I started the motor it ran for a minute and then it locked up.
I haven't tried the spark plug yet but what is exactly the crank connected to and could that have broke.?

Everything looks normal to me but I don't know Motors, and I'm wondering if whatever the sprocket crank is attached to if that broke somehow and that's what's causing the back wheel to seize because the motor is not even turning over, I can't even pedal the bike without pulling the lever for the clutch.

Active Member

Everything looks normal to me but I don't know Motors, and I'm wondering if whatever the sprocket crank is attached to if that broke somehow and that's what's causing the back wheel to seize because the motor is not even turning over, I can't even pedal the bike without pulling the lever for the clutch.

The clutch is not seized as that is always connected to the wheel, even when clutch is pulled.

His motor probably just took a dive, but a small chance the gears have stuff in them, usually you can roll it backwards a tad if it's the teeth since that's just how gears work. 1000 miles isn't bad, actually a pretty good average for these motors, I bet his wrist pin bearing turned into those magic sprinkles we all like.

New Member

The clutch is not seized as that is always connected to the wheel, even when clutch is pulled.

His motor probably just took a dive, but a small chance the gears have stuff in them, usually you can roll it backwards a tad if it's the teeth since that's just how gears work. 1000 miles isn't bad, actually a pretty good average for these motors, I bet his wrist pin bearing turned into those magic sprinkles we all like.

How many miles does a 49cc motor go? It's odd for me to believe that it was running fine and all I did was adjust the chain tensioner and then itseized, what actually seized is a question?
I think it actually has something to do maybe I pushed the rod I don't know to the piston?
Everything worked fine and great until I adjust to the tension rod and that's weird the back Wheels stopped moving when the clutch was disengaged if I'm saying that right when I pulled the lever that's the only time it will roll.
Baby when I need to do is look at the piston and self but like I said before I think it has something to do with the crank sprocket connected to the engine.

Active Member

Like even if you pull the wheel hard? The clutch plate moves off the pads when you pull the lever. Take the cover off and look at your clutch. You might need to adjust your flower nut or your clutch cable.

Well-Known Member

The motor only goes as far as it wants to, usually something like 1k is when you expect to see cylinder problems, it may have even been a ring that blew up. The problem is these things are just unpredictable and cheap, some die the same day you buy it and others (with good care and a bit of luck) last thousands of miles. Most will get to be problematic around the time yours did, if they were just built better then they would obviously last longer. Theis is why you can find 30 year old dirt bikes for sale in running condition, used well but running, they just put the f***ing time into making them right. Even those will cost more than double used than what it costs to build a motorized bike new, it's just a figure of quality, quality lasts, and good maintenance keeps it lasting longer.

Unfortunately this is the stick beating a very dead horse and turd polishing olympics type of issue, where no matter how hard you try the China girl always breaking your heart, she just doesn't want to live! (or not very rong- I mean long) the Chinese also have illegal supplies of ground tiger penis and stuff like that which apparently makes things work better or last longer, if you find some and mix it into the gasoline it may improve the mpm (milage per motor.)

New Member

The motor only goes as far as it wants to, usually something like 1k is when you expect to see cylinder problems, it may have even been a ring that blew up. The problem is these things are just unpredictable and cheap, some die the same day you buy it and others (with good care and a bit of luck) last thousands of miles. Most will get to be problematic around the time yours did, if they were just built better then they would obviously last longer. Theis is why you can find 30 year old dirt bikes for sale in running condition, used well but running, they just put the f***ing time into making them right. Even those will cost more than double used than what it costs to build a motorized bike new, it's just a figure of quality, quality lasts, and good maintenance keeps it lasting longer.

Unfortunately this is the stick beating a very dead horse and turd polishing olympics type of issue, where no matter how hard you try the China girl always breaking your heart, she just doesn't want to live! (or not very rong- I mean long) the Chinese also have illegal supplies of ground tiger penis and stuff like that which apparently makes things work better or last longer, if you find some and mix it into the gasoline it may improve the mpm (milage per motor.)

Well get crackin, just looking at the outside typing on the internet isn't going to it any good, hope you've been soaking it in pb blaster this whole time you were waiting to 'loosen it up' so you can play it off like you knew whats you was doing.

New Member

So as I stated before, it appeared something was hindering the engine to move. Well I popped off that cover on the other side of the engine and the screw in that small sprocket fell out, so what I'm thinking is if I just replace that screw that should fix the problem.
I will need a new cover plate cuz as you can see where that screw came off it damaged it the inside....
what is the proper term for this, drive train sprocket? correct?

New Member

They are metal shavings on the clutch chain side.. Inside the cover.. Not magneto cover... The screw that was in I guess the bevel gear... I'm not familiar with the proper terms of a engine . No electrical problems , Anyways.. That screw was missing thread and thats what tried to break through clutch gear plate guess its called in pic above right side.
I ordered the clutch assembly kit and a new cover should be Thursday Friday ish.

Well-Known Member

They are metal shavings on the clutch chain side.. Inside the cover.. Not magneto cover... The screw that was in I guess the bevel gear... I'm not familiar with the proper terms of a engine . No electrical problems , Anyways.. That screw was missing thread and thats what tried to break through clutch gear plate guess its called in pic above right side.
I ordered the clutch assembly kit and a new cover should be Thursday Friday ish.

Well the cover I'd of just left it go after a good cleaning and a bit of jbweld to seal against water, these things are so cheap it's not even worth trying to keep it pretty looking. That screw might be found on an old bicycle if you have one, the thread is the same as what's normally used on a crank arm for the pedals, it's the one holding the arm to the shaft (bottom bracket) with the gears on it. Those are just about always going to be a standard hex head bolt, so you can remove and install with a (usually) 14mm socket wrench, way better than a flat head screwdriver. Bevel gear is correct.

The metal shavings are unrelated to the clutch, often the chain rubs the metal under the cover, usually the section nearer the front of the motor, that creates shavings that get stuck in the grease inside the cover, it's kind of normal and impossible to avoid unless you go and shape it down with a dremel. I would give the entire chain, drive gear cover, and rear sprocket a good cleaning with a rag and solvent to get the metal off it, that stuff will get into the chain, and on the other meshing gears and act like sandpaper and rip up the gears and chain, wearing them down and 'stretching' the chain, which furthers the wear on the gears more.